Grasses & forbs

The herbaceous native plants of grasslands are my greatest ecological interest.  To be able to restore a degraded native pasture to wildflower glory is my holy grail.

Phenology (fen-ollo-gee) –  the emergence from winter and awakening of plants and people
Early Nancies – the incomprehensible sex life of this diminutive wildflower.
The autumn colours of grass – who needs deciduous trees?
 


Phenology (fen-ollo-gee) – September 2013
I am writing this in the last week of winter, and the cheery wattle blossoms and the hesitant purple pea flowers of Hovea and Hardenbergia have revealed themselves.  To my mind,  they represent the last phases of winter rather than spring.  The true harbinger of spring is when the Early Nancies(Wurmbea dioica) come out.  These modest white lilies have attractive purple markings and flower optimistically after producing two tremulous thin leaves. They do best where the grass is very short and there is some bare ground.  They flower and set seed while most other species are thinking about it.

Early Nancies provide the hors-d’oeuvres for the  delicious procession of  lilies and orchids and other wild flowers that come and go between September and December.  The days of spring are precious if you want to observe all the forbs whose flowers come and go.  Pay close attention and take frequent walks.  Those that ignore the bush for few weeks in October, will find that whole flowering cycles will elude them.  Many orchids grow only one tiny leaf a year, and if you  miss the flowers, that’s it for another twelve months, apparently no orchids.

Using the flowering and seeding cycles of plants to read the physical environment and predicting reproduction from the weather are ancient practices linked to food gathering and survival of all humans.  What we have done naturally for eons has now morphed into a science called phenology.

Not to be mistaken for phrenology, the now discredited scientific discipline of interpreting how the shape of your head determines your mental powers, phenology is a perfectly respectable branch of science that has become more prominent of late.  It is simply the observation of the annual life cycles events of plants (growth, flowering,  seeding)  and animals (migration, mating, breeding) and their relationship with the physical environment.

The attention to phenology has arisen from interest in tracking possible responses of plants and animals to climate change.  Because written records of biological events have been collected since the 18th century, phenological data sets are among the few long-terms observations in existence and are a valuable way of detecting more recent changes.  Observations of the first flowering, the first arrival of a bird species and so on, are relatively simple to collect.

Amateur naturalists have been great contributors to the field of phenology.  One example is Richard Fitter whose observations of flowering made it into the leading journal Science providing the strongest available evidence of climate change in 2002.  Fitter’s data showed that the average first flowering date for British plant species in the 1990’s was 4.5 days earlier than the average first flowering date over the preceding forty years.

I have not been around long enough, or been disciplined enough in recording my observations of flowering to observe this kind of “season creep” in Gundaroo.  Flowers and flowering is a topic where I have neglected to make any formal records, choosing rather to indulge myself in the fleeting moments and enjoy just looking.

Despite my laziness, the tradition of collecting phenological data continues with renewed interest, with the assistance of the internet and fuelled by concerns about climate change.  There are a number of web sites seeking to capture the observations of citizens and gain from the observations of many.  Participation in projects like these can help sharpen vague observations into useful data.  Opportunities extend beyond plants to birds and to just about any organism  you might be interested in, including fungi.

The main thing is to be out there, looking and enjoying.  Plants are not the only ones gearing up in spring, I notice my friends seem to shake off their winter  torpor and start organizing social events in spring, which make me wonder sometimes why we do not have more mid-winter festivities and leave spring for the study of phenology.


 


Early Nancies – October 2014

I know that I go on about Early Nancies, the harbingers of spring and all that, but it really has been the most brilliant season for this wonderful wildflower, I can’t help but write about them again. A small lily, it has only two leaves and its single flower spike emerges in early September.  It likes a short grass lawn, and grows through winter.  Clearly the good autumn winter rains this year have favoured it.  I can barely put a foot down on our front lawn without treading on one.

The only ugly thing about Early Nancies is their latin name – Wurmbea dioica – I am not even going to try and give you pronunciation tips, because I actually don’t have any.

I was a post-graduate in the 1980s when our lab was visited by an English botanist from Canada. Spencer Barrett did research on rice weeds (my topic of study) but also had an interest in the evolution of plant reproductive systems.  It was Spencer who drew my attention to the mysteries of the Early Nancy, as he had come out to Australia specifically to observe their flowers.

Most plants have flowers that are bisexual, with both female ovaries and male anthers together on the one flower.  However, about 6% of plant species have flowers of different sexes – male flowers with pollen-bearing anthers, and females flowers with ovaries (which set seed once pollinated).  It was a source of great interest to Spencer as to why, and how, this separation of male and female flowers evolved.  And it turns out that while Early Nancies have flowers of separate sex, they can also have in-between states.  In some places, there are three types of flower spikes: all male, all female, and ones with bisexual flowers at the base plus males on top.

The dioecious Early Nancy. On the left, the dark bulging ovaries can be seen on the female flowers, and the dark bands indicating to insects where the nectar is located.
On the right, the ovaries are barely visible and there are anthers bearing pollen. The nectar markers are much paler. These differences are easily seen with the naked eye.

By observing how the gender ratios of the flowers vary in different habitats, clues can be gained as to how and why dioecy (the separation into male and female plants) might have evolved.  Apparently Early Nancies provide a case study worth crossing the globe to pursue, and it turns out that dioecy may confer an evolutionary advantage in dry, infertile habitats.

Since his days crouched over early Nancies in the foothills of the Brindabella Ranges, Spencer Barrett has gone on to a brilliant and distinguished scientific career on the evolution of plant reproductive systems. He has supervised students in their study of Early Nancies, and is an author of many of the 40+ research papers that discuss the wonders of their reproductive system – although the wonders are admittedly somewhat buried in terminology and hard to distil.

These days, I email Spencer twice a year – first on his birthday, which is the same date as mine and therefore easy to remember. And second, in Nancy season, when I take the opportunity to send a photo that shows off our fabulous annual display of his celebrity flower.

 


The autumn colours of ….. grass? – July 2014

Autumn colour is a great source of fascination to the human race.  Tourist industries are built upon this particular obsession, particularly in parts of North America, although in cooler parts of Australia attempts are also made to cash in on this interest in the colour of dying leaves.  Canberra and Bright (Victoria) are notable amongst them.

Most of us realize that leaves are green because they contain chlorophyll, and chlorophyll uses sunlight, water and carbon dioxide to make carbohydrates.  That is why plants are called primary producers, they make food from scratch (or a least water and air).  Almost every other life-form depends on this photosynthesis to produce the carbohydrates so vital for life.

When winter approaches and it’s getting too cold and dark to photosynthesize efficiently, deciduous plants stop making the green pigment called chlorophyll.  They do this by gradually choking off the supply of nutrients and water to the leaves through accumulation of cork cells in the base of the leaf stalks.  When the plug of cork is complete the leaf eventually falls.

The progressive decay of the chlorophyll reveals orange, yellow and brown pigments that are already in the leaves, but are hidden in summer by green.  As the tree continues to drain the nutrients, the leaves start making red pigments known as anthocyanins.  The red colour that people love so much appears to be largely a by-product of the leaf shutting down, and its use to trees is not well understood.  Sunny autumn days without frost make the reddest leaves.

The problem with deciduous trees is that you have to live with lifeless sticks for the rest of winter.  It’s a bit like the delayed gratification test they do on kids to determine their emotional intelligence  – one marshmallow now or two marshmallows later?  An immediate blaze of colour now, or soothing green foliage to enjoy all winter?

Having grown up literally in the canopy of an elm forest, you’d think I might have some affinity with deciduous trees, but no, I prefer the year-round green foliage of the eucalypt over an autumn dump of yellow leaves.  The yard maintenance was too off-putting for a teenager – leaves in the gutters, on the paths and my parents even installed a swimming pool in the elm forest.

Nowadays I get my autumn pleasure from grass.  Showing a friend our native grassland on Gang Gang a while ago, I was impressed when she pointed out the glorious autumn colours of the grasses as they approached dormancy.  It is now a highlight of the year.

My current computer wallpaper is a kaleidoscope of mellowing green blending into golden yellows giving ways to intense oranges and delicate pinks.  These are the colours of an autumn perennial grassland glowing in the midday autumn sun.  Because the native grasses are predominantly summer-growing species, they shut down in the cooling temperatures and shortening days in much the same way as deciduous trees.  Their colours can be quite intense, but in this photo they are a magical balance of gentle pastels glowing intensely in the light.

Sadly, these glowing pigments too will break down in the same way as autumn leaves, except the grass leaves remain attached to the plant.  Over winter they will fade to brown and then grey, becoming increasingly bleached as they make their way to being eventually organic matter in the soil or fuel for a fire.  So if you have any remnants of autumn colour in your native grasses, enjoy them now, as while the mild spring has delayed the autumn, they will be fading before your eyes.

Interestingly, it is the winter-growing introduced pasture grasses and weeds that provide the soothing greens over winter – providing the frosts don’t fell them and rainfall permits their growth.  Gang Gang in August would be grey and somewhat depressing if it were not for the cheery flowering wattles and the promising buds of the yam daisies.